Correct Answer - Option 1 : 1.21 Ohms
Concept:
Base impedance is given by
\({Z_{base}} = \frac{{kV_{base}^2}}{{MV{A_{base}}}}\)
kVbase is base voltage rating
MVAbase is base MVA rating
Calculation:
Given that, base kV = 11 kV
Base MVA = 100 MVA
Base impedance, \({Z_{base}} = \frac{{{{11}^2}}}{{100}} = 1.21\;{\rm{\Omega }}\)
Important:
The relation between new per-unit value & old per unit value impedance
\({({Z_{pu}})_{new}}\; = {({Z_{pu}})_{old}} \times {\left( {\frac{{k{V_{base}}}}{{k{V_{new}}}}} \right)^2} \times \;\left( {\frac{{MV{A_{new}}}}{{MV{A_{old}}}}} \right)\)
Also \({Z_{pu}} = \frac{{{Z_{Actual}}}}{{{Z_{base}}}}\)
\({Z_{base}} = \frac{{kV_{base}^2}}{{MV{A_{base}}}}\)
Where,
(Zpu)new = New per unit value of impedance
(Zpu)old = Old per unit value of impedance
kVbase = Old base value of voltage
kVnew = New base value of voltage
MVAnew = New base value of power
MVAold = Old base value of power